1. Field of the Invention
The present invention relates to an image processing apparatus for controlling copy operation by embedding information for copy inhibition or information for tracing print-out operations, and by extracting the information thus embedded.
2. Description of the Related Art
With the development of IT technology in offices, there has been an increasing concern for security in recent years. For example, cases of leakage of corporate customer information have frequently occurred, and such threatening of personal privacy has become a great social problem.
To deal with such problems, measures for preventing information leakage to the outside of a firm have been taken in general, for example, by controlling an access right to digitized confidential information and by installing a monitoring device for a firewall. Moreover, there is a measure in which portable media such as a notebook computer or a USB memory are forbidden to be carried into and out of an office. In the case of digitized confidential information, corporate customer information can be protected by determining and implementing monitoring policies, as described above. However, when confidential information is printed on a paper medium with a printer, it is considered to be more difficult to check or forbid the carrying-out of the paper medium on which personal information is printed, than to restrict the carrying-out of digitized confidential information. This makes it difficult to maintain security.
To ensure security of printed material, there is a copy restriction technology (e.g., Japanese Patent Laid-open No. 2003-280469) in which information on copy permission or copy inhibition of a printed material under a particular condition is embedded in an original document in the form of a dot pattern or a bar code so that copy is restricted. Further, there is a tracking technology (e.g., Japanese Patent Laid-open No. 2003-205661) for tracking persons who make copies. In this technology, copy inhibit information and information indicating a place where copy history information is embedded are embedded into a digital watermark of a type embedded into the entire surface of a sheet of paper.
In the tracking technology of Japanese Patent Laid-open No. 2003-205661, in addition to a digital watermark, an editable bar code and image position information of the bar code are embedded into the digital watermark. At the time of copying, the image position of the bar code is identified from extracted digital watermark information, and it is determined whether the bar code is embedded at that position. In this technology, when the bar code is not embedded at that position, copying is prohibited as a fraudulent copy.
However, in the above-described conventional technologies, there is a problem that an embedding area of copy history information is fixed at the first print, and may eventually run out of its information capacity as copies are repeatedly made.
Meanwhile, as to the above-described problems, the shortage of the information capacity of the embedding area of copy history information can be avoided by adding an embedding area of copy history information at the time of copying. However, it is not possible to detect a falsification of the embedding area of copy history information without determining, for each copy, how the embedding area has been added. To manage copy generation information for paper copies, it is necessary to prevent copy history information from being falsified.